1. Field of the Invention
The field of the invention is primarily that of means for generating electrical current. More particularly, the invention is concerned with a form of thermopile, that is a plurality of series connected thermocouples. Although thermopiles have wide utility, the improved construction of this invention is particularly adapted for use as a generator for generating an electrical signal in response to heat from a pilot flame in gas fired or other installations.
2. Description of the Prior Art
The relevant prior art is found primarily in the field of pilot generators utilized in gas fired heating systems. A form of pilot generator embodying a thermopile has been in use for many years. This particular form consisting of first and second groups of dissimilar metals arrayed in a circle and positioned against the inner side walls of a metal tube or sleeve. In a common form of the device, the elements were in the form of flat metal bands with the hot and cold junctions being provided by way of welds at the ends between the flat end surfaces of the bands, the hot junctions being at one end and the cold junctions at the other. Typical dimensions of this type of construction are, of course, known in the art. In the known commercial constructions typically there have been in some instances 27 thermocouples and in others 30 thermocouples. The prior art constructions described above were subject to some drawbacks. Heat transfer from the outside of the sleeve or jacket to the thermopile elements was less efficient that desired. In one construction, the thermopile elements were arranged in a spiral with part of the elements in the interior of the tube or sleeve resulting in reduced heating efficiency. The response time of the prior art constructions was not as rapid as desired, for example, the time was in the order of 10 to 15 seconds or slower as the time required for the thermopile to produce sufficient power to operate a valve.
Additionally, the prior art constructions were very difficult to fabricate, requiring complicated fabricating machinery, particularly for purposes of making welds between side portions of the ends of adjacent elements.